<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>

    <style>
      .circle {
        width: 100px;
        height: 100px;
        border-radius: 50%;
        background-color: pink;
        margin: 10px auto;
      }

      .semicircle{
        width: 100px;
        height: 50px;
        border-radius: 50% 50% 0 0 / 100% 100% 0 0;
        background-color: pink;
        margin: 10px auto;
      }

      /* 
        x表示椭圆水平半径  
	    y表示椭圆垂直半径 
        border-radius: x/y;
        */
      .oval {
        width: 100px;
        height: 50px;
        border-radius: 50px/40px;
        background-color: skyblue;
        margin: 10px auto;
      }
    </style>
  </head>
  <body>
    <div class="circle"></div>

    <div class="semicircle"></div>

    <div class="oval"></div>
  </body>
</html>
